In the casting arts, molten metal is poured into a mold through an opening in the top of the mold with a certain excess metal filling the channel to the mold cavity. When multiple parts are cast in the same casting vessel, the mold will include channels in the form of a sprue to each cavity for each part, which will create undesired dross on the outer surface of the casting once the molten metal has hardened into the casting. The excess metal, such as those referred to as risers or gates, is frequently required to be removed by a cutoff or grinding operation in order for the casting to perform the purpose intended.
There are several common practices used by foundries to remove the risers or gates from the castings. These practices include, but are not limited to, removal of the riser by means of a gas torch, a grinder, a conventional cutting blade or saw, or some similar machine for forcefully removing the dross. Moreover, after the gates or risers have been removed from the casting through any of these methods, the operator commonly has to further grind or finish the casting due to an uneven cut caused by the respective trimming method.
The most common practice of cutoff operation is conventionally done either by an operator controlling a machine having a cutoff blade or automatically by means of a robotic device having a cutting blade. In the first example, the operator controls the machine that applies a cutting force that may come from an external force, such as a hydraulic cylinder, or it may be generated manually by the operator physically controlling the cutting force with his own strength and weight. In the second embodiment, the robot may be used to hold the casting to engage a fixed cutoff saw, or to the contrary the robot may hold the cutoff saw while the casting is in a fixed position.
Robots have been used for years to control the movement of a casting through a cutoff blade. In addition, hydraulic, pneumatic or electric cutoff saws have also been used in the common foundry to push the blade (or casting) through the casting (or blade). However, these solutions incorporating the use of the robot experience inherent problems. For example, one inherent problem with the use of the robot to control the cutoff operation is that the cutting wheel will have a short abrasive life. In addition, this solution requires a long robot cycle time to cut the riser. Moreover, significant heat is generated in the casting in such a method due to incorrect cutting force or pressure. Cutting forces that are lower than that prescribed by the blade manufacturer can cause excessive heat in the blade and the material being cut. These high temperatures in the material can degrade the properties of the material, resulting in scrap or wasted castings. Finally, there is frequently an inconsistent cut in the casting due to deflection and vibration in the robot, which could lead to possible damage to both the robot and the cutoff saw due to inconsistent gates or risers.
What is desired, then, and not found in the prior art, is a compliant cutoff saw assembly having a design that will accurately and efficiently cut a casting supported by a constant force or pressure as chosen for the particular casting to maintain the integrity of the casting and the functionality of the assembly.